1. Technical Field
The present invention relates to a contrast correcting circuit. More specifically, the present invention relates to a contrast correcting circuit suitable for use in a display device having a small dynamic range, such as a plasma display panel (PDP).
2. Related Art
A contrast correcting circuit for emphasizing the contrast of areas in a picture having a large amount of information is commonly used in a display device having a small dynamic range, such as a plasma display panel (PDP). Such a contrast correcting circuit ensures a higher quality picture.
In a conventional contrast correcting circuit, a plurality of different types of look-up tables containing varying contrast conversion characteristics are used for converting a contrast in order to emphasize the contrast of a picture. The tables are stored in a memory such as a read only memory (ROM). The result of integrating picture data for a screen, or the result of obtaining a histogram, is used for selecting such look-up tables.
Excellent images are obtained on most screens when a conventional contrast correcting circuit that converts the contrast of picture data using a plurality of look-up tables is used.
However, there are instances when it is better not to correct the contrast. In particular, picture data of a dark screen in a movie should not undergo contrast conversion. When there exists a small area having a relatively bright image in a picture having a large number of pixels of a black level, because much of the picture is formed of images that are realized using pixels of the black level with respect to an area ratio (that corresponds to the amount of data), a look-up table having a contrast conversion characteristic that is effective in a dark screen is easily selected in the conventional contrast correcting circuit.
However, when there exists a small area of a relatively bright image in a picture having a large number of pixels of a black level, important information is included in the small area of the picture. When the contrast is corrected in such a screen by selecting the look-up table for a dark screen, deterioration such as white distortion easily occurs.